Safety stop for presses



July 2, 1963 P. J. LINDNER SAFETY STOP FOR PRESSES Filed June 14.

INVENTOR. v/z/ J, z//Va//ff BYMMW` 3,095,804 SAFETY STOP FOR PRESSES Philip J. Lindner, Mount Gilead, Ohio, assigner to Koehring Company, Milwaukee, Wis., a corporation of Wisconsin Filed June 14, 1960, Ser. No. 35,973 8 Clmfrns. (Cl. 10G-53) This invention relates to presses, and particularly to a safety stop to support the platen or moving weights of vertical downward acting presses.

Vertical presses for metal Working punching `and other similar operations may often employ a ram and platen Ithat weigh many tons. Various types of safety jacks and stops have been employed in the prior art to prevent accidental dropping of the platen while it is in a raised position so as to prevent damge to material, personnel and the press itself. Some of the disadvantages of these prior devices are that they interfere with the daylight opening of the press; they are independently engaged in operative position; and they may be damaged if not disengaged during a working stroke of the platen.

Therefore an object of the invention is to provide an improved safety stop for a press of this type which will be automatically engaged whenever the platen is in a full raised position or whenever the press is stopped with the platen in any raised position.

Another object is to provide an improved safety stop arrangement that safeguards the operator and material without interfering with the Working :area of the press.

Another object is to provide a safety stop device that will be automatically disengaged during a normal intended working stroke of the platen.

Still another object is to provide a safety stop device that will not be Vdamaged if it fails to `disengage on a normal power actuation of the press platen.

These and other objects and advantages will be apparent to those skilled in the art from the following description of the invention as shown in the drawings, in which:

FIG. l is a schematic representation of a hydraulic press, partially broken away to show the position of an apparatus embodying the present invention with respect to the press and parts thereof;

iFIG. 2 is an enlarged side elevational view, partially in section, with :appropriate parts broken away, showing details of the safety device embodying the present invention; and

FIG. 3 is a top View, slightly enlarged, taken substantially along line 3 3 of IFIG. 2, partially in section, with certain parts removed for clarity, and showing a diagrammatic representation of a hydraulic valve for activating the apparatus embodying the invention.

While the invention may be variously modilied, the preferred embodiment has been shown in the drawings and will be described hereinafter in detail. -It should be understood that there is no intention to limit theI invention to the specific form disclosed; but it is intended to cover al1 alternative constructions falling within the spirit and scope of the invention as expressed in the claims appended.

In FIG. 1 of the drawing, there is shown in schematic form a hydraulic press 10 having a frame .11, a press bed 12, a press head 113 and a ram 14 -and platen 15 for vertical downward working movement. The electrical and hydraulic control mechanism and circuits for such presses are well known in the art and are not shown.

Stop rods 21 are iixedly attached, preferably by bolts, to diagonally opposite corners of the platen at 22. The stop rods 21, which extend through the press head `13, have a threaded portion 23 at the upper end. (Only one rod shown in broken away portion.) The rods 21 move assista Patented July 2, 1963 vertically corresponding with movement of the platen 15.

As seen more clearly in FIGS. 2 land 3 a circular wheel or nut 311 engages the threaded portion .23 of each rod 21. The nut 31 is held in a vertically fixed position on the press head `13, between bearing plates 35, 316, which are both axed by suitable thru-bolts 37 to the press head 13. Between each bearing .plate -and the upper face and lower face of the nut 31, roller bea-rings 38 are mounted. These bearings 3S may be of any suitable commercially available stock such as Timken Bearing, type TIHD. Although restricted in vertical movement the nut 31 is free to rotate or spin on the threaded portion 23 of the rod 21, as the rod 21 moves upy or down with the platen 15. yOn the outer circumference of the nut -31 is a wear band or drum 32 held in place by a key 33. In order to enable the nut to freely spin in both directions lead must be carefully selected. It must be great enough so that the thread is not self-locking and must remain small enough so that -a reasonable size brake, hereinafter described, will be able to hold the nut from spinning. In the embodiment disclosed the 5" nut and shaft have 4 Acme threads, 11/3 threads per inch or a 3A pitch, thus a lead of 3 inches.

Surrounding the drum 32 on each nut 31 is a brake band assembly 41, comprised of two parts pivoted at 43, the inner circumference of the band having a lining 44. Opposite the pivot each part of said brake band has an ear or lever arm, 4'5 and 46.

A spring 51 is employed to normally urge the two par-ts of said band 41 together about pivot 43 and set the brake about the drum 32 which is part of nut 31. A stud 50 is threaded at one end to lever arm 45 at 52 and held by lock nut 53. The stud 50 passes through the lever arm 46 on the opposite half of the brake band at 54 and the spring 51 is slipped over the stud 50 Iand `secured by washer 55 and nut `56 at the outer end of the stud 50. Tension of spring Sil may be increased or decreased by adjustment -of nut 56. A's long as spring 51 is in compression the brake bands 41 are set and the nuts 31 cannot rotate thus preventing movement or dropping `of rods 2l and the moving Weights or platen 1'5.

A cam arrangement actuated by a hydraulic cylinder 61 is employed Ito compress the spring 51 and release the brake band 41. The hydraulic cylinder 61 is pivotally connected at 62 to an arm 47 on one part of the brake band 41. The piston rod 63 of said cylinder 61 is pivotally connected at '64 to one end of a bell crank or cam arm 65 which is pivotally connected at 48 to lever arm 46. Two cams 66 are located at the opposite end of the arm 65. Two lugs or `cam Ifollowers 49 are located -on lever arm 45y so as to be engaged by cams 66 on clockwise movement of cam arm 65 about pivot connection 48 outward movement of piston rod 63 of the hydraulic cylinder 61. Engagement of the cam followers 49' and cams 66 will urge the two parts of brake band 41 to open about pivot 43, compressing the spring 51 and thus releasing the brake and allowing nuts 31 to spin upon movement of rods 21.

In FIG. 3 a schematic valve arrangement is shown for control of hydraulic iluid operating cylinder. lt is understood that there are two braking` arrangements and the valve shown will control uid flowing to both brake systems. Line 81 connects the piston or large area of the cylinder with valve while line 82 connects the differential area or pullback side of the cylinder with valve 80. Line 83 leads from valve 80 to a pump (not shown) supplying auxiliary or pilot fluid pressure independent of hydraulic iiuid pressure serving the press ram 14. Line 84 leads from the valve 80 to a reservoir (not shown). Valve yS0 is a four-way valve actuated by a solenoid 90 and returned to the position shown by a spring 91.

The brake bands 41 are kept from cooking by extensions of the pivot connections 43 and 48 which substantially tit between bearing plates. (Extensions 48a shown in FIG. 2 on pivot connection 48.) A stop 42 may also be bolted to the lower bearing plate 36 (FIG. 3), which engages a guide 42a on brake bands.y

Having explained the drawings a cycle of operation will now be described. A Assuming the press platen 15 is at its uppermost position the spring 51 will automatically set the brake bands 41 as shown in FIG. 3 to prevent the nuts'31 from turning and thus support by rods 21 the platen 15 and other moving weights.

The valve '80 as shown is in position to admit pilot pressure fluid to the pullback side of cylinders 61 through line 82.-. When an electrical signal is given for the press platen 15 -to descend the solenoid 90 is energized. The solenoid 90 moves valve 80 downward as shown in the drawing so as to admit pilot pressure iiuid to the piston area of the cylinders through lines 81, 83 while uid from the pullback area returns to the tank through 82, 84. Cam arm 65 will be rotated by the piston rod 63 thus moving cams 66 into engagement with cam followers 49 thus forcing brake bands 41 open against spring 51. This releases braking force on the nut 31 which will spin at a speed determined by descent of platen 15 which is controlled by pump stroke of the hydraulic system actuating ram 14.

The solenoid 90 stays energizedv thus holding brake bands 41 open until the platen 1S has again returned to its top position or the press is stopped by the operator. If the press is stopped or the platen 15 returns to its top position the solenoid 90 will no longer be energized and spring 91 will return Valve 80 to the position shown. This will admit pressure iluid to the pullback side of the cylinder 61 and allow tluid from the piston side of cylinder 61 to return to the tank. The'pullback of piston rod 63 will expedite the release of the cams 66-and the spring `S1 will again set the brake bands 41 to prevent nuts 31 from rotating and support the rods 21 and thus the' platen 15 so as to avoid accidental dropping due to hydraulic pressure or other failure in ram 14. t

If at any time lthere is an electrical or pilot pressure failure the brake bands 41 would be automatically set by spring 51 which would bring the platen 15 to a stop.

What is claimed is:

1. In a press having a frame member, a relatively movable platen member and hydraulic means for actuating vsaid platen member, a safety stop device auxiliary to said actuating means comprising threaded nut means ailxed to one of said members; threaded shaft means aixed to the other of said members and having threaded engagement with said nut; said nut and shaft being relatively rotatable when one is moved axially with respect to the other; one of said threaded means being non-rotatably atxed to its respective member; and brake means for selectively preventing relative rotation between said nut and shaft thereby preventing further movement of said platen member.

2. In a press having a frame member, a relatively movable platen member and hydraulic means for actuating .said platen member, a safety stop device auxiliary to said actuating means comprising threaded nut means aixed to one of said members; threaded shaft means axed to the other of saidfmembers and having threaded engagement with said nu-t, said nut and shaft being relatively rotatable when one is moved axially with respect to the other; one of said threaded means being non-rotatably afxed to its respective member; brake means for normally preventing relative rotation between said nut and saidshaft thereby preventing movement of `said platen member; and means for releasing said brake means upon actuation of said platen member.

3. lIn a press having a frame member, a relatively movable platen member having -an actuating ram, and means for actuating said ram, a safety stop device comprising a threaded rotatable nut aixed axially to said frame member; a threaded shaft non-rotatably aliixed to '4 said platen member and threadably engaging said nut, said nut being rotatable when said shaft is moved axially with said platen; a brake normally coacting with said nut for preventing rotation of said nut thereby preventing movement of said platen; and means for releasing said brake upon actuation of said ram.

4. In a vertically acting press having a frame and a reciprocably movable platen, a safety stop device comprising a rod non-rotatably aixed to said platen; said rod threadably engaging a rotatable nut xed in a vertical position on said press frame; brake means coacting with said nut for restricting rotation thereof; thereby preventing movement of said platen; and means for releasing said brake means.

5. In a press having a frame and a vertically movable platen actuated by a ram, and actuating means for said ram, a safety stop device comprising a threaded rod nonrotatably fixed to said platen; said rod threadably engaging a rotatable nut fixed axially with respect to said press frame; brake means coasting with said nut; yieldable means normally setting said brake means thereby preventing movement of said rod and platen; and means for releasing said yieldable means upon actuation of said ram.

6. In a4 press having a frame and a vertically reciprocable platen actuated by a ram, and actuating means for said ram, a safety stop device for saidr platen comprising a threaded rod non-rotatably ixed to said platen; said rod threadably engaging a circular rotatable nut fixed in a vertical position to said press frame; a brake band coacting with said nut; spring means normally setting said brake band around said nut; and means for releasing said spring means and said brake band upon actuation of said ram.

7. In a press having a frame and a vertically reciprocable platen actuated by a hydraulic ram, and means for actuating Isaid ram, a safety stop device for said platen comprising a plurality `of threaded rods non-rotatably iixed to said platen; each of said rods threadably engaging circular rotatable wheels lixed in a vertical position to said press frame; said wheels including a brake drum on the outer circumference thereof; an cX- pandab'le brake band surrounding said brake drum; spring means normally setting said brake band on said drum thereby preventingrnovement of 'said rods and platen; and hydraulically actuated means for releasing said brake band from said drum upon` actuation of said ram.

8; Infapresshaving a frame, a head, and a vertically reciprocable platen actuated by a hydraulic ram, and means for actuating said hydraulic ram, a safety stop device for said platen comprising, a plurality of threaded rods non-rotatably ,fixed to said-platem-each of said rods threadably engaging circular rotatable Wheels xed in .an axial position by bearing plates to said press head, said wheels including a brake drum on the outer circumference thereof; expandable brake bands surrounding said brake drums; spring means normally setting said brake bandsY on said drums whereby rotation of said/wheels is prevented thus holding said'rod-s and' said platen in a fixed position; cam and lever means for expanding said brake bandsl against said spring means; hydraulic cylindersV for acting said cam and lever means; pilot pressure tluid for actuating said cylinders; and a solenoid valve actuated simultaneously with said actuating ram for controlling ilow of pilot'pressure to said'cylinders.

References Cited in the file of this patent UNITED STATES PATENTS 642,501 Snyder Ian. 30, 1900 808,041 Gormley Dec. 19,'1905 1,934,984 Loshbough Nov. 14, 1933 2,164,245 Kienzle l une 2,7, 1939 2,192,734 Clouse Mar. 5, 1940 2,844,969 Lohr July 29, 1958 

1. IN A PRESS HAVING A FRAME MEMBER, A RELATIVELY MOVABLE PLATEN MEMBER AND HYDRAULIC MEANS FOR ACTUATING SAID PLATEN MEMBER, A SAFETY STOP DEVICE AUXILIARY TO SAID ACTUATING MEANS COMPRISING THREADED NUT MEANS AFFIXED TO ONE OF SAID MEMBERS; THREADED SHAFT MEANS AFFIXED TO OTHER OF SAID MEMBERS AND HAVING THREADED ENGAGEMENT WITH SAID NUT, SAID NUT AND SHAFT BEING RELATIVELY ROTATABLE WHEN ONE IS MOVED AXIALLY WITH RESPECT TO THE OTHER; ONE OF SAID THREADED MEANS BEING NON-ROTATABLY AFFIXED TO ITS RESPECTIVE MEMBER; AND BRAKE MEANS FOR SELECTIVELY PREVENTING RELATIVE ROTATION BETWEEN SAID NUT AND SHAFT THEREBY PREVENTING FURTHER MOVEMENT OF SAID PLATEN MEMBER. 